Depending which ISP you are with you can turn on there spam filter. Optus do it for free where as Tel$tra charge for it.
That should help but won't stop all of it. Have a look at Mailwasher. It allows you to use spam blocking lists and setup your own filters to automatically delete messages before your mail client downloads them.
I use this and have a few filters setup to delete anything with keywords like Viagra, cock etc etc.
Seems like most of my spam comes from China as over Chinese new year my spam stopped.
You will also find Mailwasher on torrent sites
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